I'm so sorry OP. Daughter of a recovering alcoholic here. At exactly the same age as your late ex, my Dad went to rehab. That was 36 years ago. He's nearly 91'now. The 3 other guys in the program all relapsed and died soon after.
None of us children drank because of what we went through with him.
He was a highly successful pillar of the community and back in the 80s you could be an alcoholic and function extremely well. All his friends and family made excuses for him.
"Great craic"
"Life and soul of the party"
"A character"
"Likes a drink, so what?"
Once he quit they were quick to tell us they'd all been worried about him and were delighted to see him sober, then one by one slowly peeled away, turned out he was also PAYING for the party.
We joined al Anon and it was fantastic, also we had family therapy, unusual for the 80s in Ireland, but it was extremely helpful.
I wish you luck on your journey. I know a little of what you're feeling.